Fish's re-grown heart gives hope for humans

A brightly-coloured fish used for studying the function of human genes can completely re-grow its heart tissue after major injury, a US team has discovered. This remarkable finding could lead to human cures for the damage caused by heart attack or heart disease.

A team led by Mark Keating at Harvard University, Massachusetts, cut out about 20 per cent of the muscle of the lower ventricle in the zebrafish. After one week, the fish were as active and could swim as well as uninjured fish. After two months, all the lost heart tissue had regenerated.

Although there is evidence that specialised heart muscle cells - cardiomyocytes - in a human heart can multiply after injury, the lost muscle does not regenerate. Instead, scar tissue forms and this can impair the heart's pumping ability.

Keating's team found that zebrafish quickly produce vast numbers of new heart cells after injury, and this rapid cell proliferation seems to prevent scarring and allow tissue regeneration.

Gene regulation

The team then went on to identify one gene that seems to be essential for the muscle cell proliferation - but they expect there will be many more. It is "almost certain" that there is a very similar gene in people, Keating says.

"The difference is probably in gene regulation. And I'm very optimistic that by altering gene regulation we'll be able to regenerate heart tissue in people," he told New Scientist.

The finding "should open up exciting new avenues for studying heart regeneration," agree Ian Scott and Didier Stainier, at the University of California, San Francisco, in a commentary on the work in the journal Science.

New fins

Scientists already knew that the zebrafish can regenerate spinal cord, retina and fins. Some amphibians, including newts and salamanders, are also known to be able to regenerate some organs and tissues. "But this is the first study that unequivocally shows cardiac regeneration," says Keating.

Zebrafish are widely used as a model for studying human gene action. Both species share similar blood, kidney and optical systems.

A team at the Sanger Institute in Cambridge, UK, is currently sequencing the zebrafish genome. This genetic blueprint should help researchers discover more genes important for heart cell proliferation after injury, Keating says.

Other teams are working on experimental treatments for damage after a heart attack, including injections of stem cells and adding muscle grafts over damaged areas. But scarring is still a problem, says Keating: "These approaches may be effective but none of them are ideal."

Journal reference: Science (vol 298, p 2188)

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